Which of these numbers is composite? ${27,\ 29,\ 47,\ 67,\ 79}$
Solution: A composite number is a number that has more than two factors (including 1 and itself). 29, 47, 67, and 79 each have only two factors. The factors of 27 are 1, 3, 9, and 27. Thus, 27 is the composite number.